Research Of Metamaterial Covers And Its Application In GPR Antenna

With the increasing demands of human beings on urban construction and the exploration of natural environments in 21 st century,the detection depth requirements of the GPR(Ground Penetrating Radar)are becoming more and more high.As most of the traditional GPR have low gain and can only be used for shallow geological structures,it is necessary to greatly increase the gain of GPR.Antenna,as one of the main implementing components of GPR,can now be used in combination with the metamaterial to achieve the performance improvement under the condition that its structure does not make a big change.Metamaterial covers,based on its different properties from lenses,absorbers and reflectors,has a good effect on improving the origin antenna gain and directivity.Cause that there is less research about this now,so this paper will explore the performance of metamaterial covers for GPR antenna,and then reveal the performance mechanism of such structure.The research content completed in this paper are as follows:(1)Research about non-gradient metamaterial covers and its application in GPR antenna.This part designs a non-gradient metamaterial covers based on antipodal Vivaldi antenna.The measurements show that the proposed antenna has a peak gain of 16.5 d Bi in 1.5-8 GHz,the half power beamwidth(HPBW)in H-planes is reduced although the results are not well in E-planes and low frequency band.(2)Research about gradient metamaterial covers and its application in GPR antenna.An effective permittivity gradient in the horizontal direction metamaterial slabs covered antipodal Vivaldi antenna is designed in this part.Its biggest gain in 1-11 GHz is 17.67 d Bi,antenna gain in1-3 GHz is effectively improved although the increment is not large and the HPBW in E-planes shows a fragmented distribution.In order to solve the above problems,this paper proposed a new Vivaldi antenna with bilayer metamaterial covers.The measurements here show that the operation band of proposed antenna is 1-8 GHz,the peak gain here is 18.2 d Bi,the HPBW is decreased in both E-planes and H-planes which decrement is larger than before.But the drawback of this structure is that it causes an increase in volume of proposed antenna.(3)Research about the combination of non-gradient metamaterial covers and lens and their application in GPR antenna.This part design a modified antipodal Vivaldi antenna with metamaterial covers and lens.Results show that the biggest gain in 1-8 GHz is 18.81 d Bi,the increment is 9 d B,the HPBW of proposed antenna in E-planes and H-planes is decreased significantly.The performance of antenna is best here.By using different forms of metamaterial covers,this paper effectively enhances the GPR antenna gain and directivity in the target frequency band,the working mechanism of the metamaterial covers is effective explored,the feasibility of this kind of structure is verified,which provides some references for improving the depth detection capability of the GPR at this stage.